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Is AD compliance ever physically verified when maintaining an aircraft?
As we all know around here, national aviation authorities put out Airworthiness Directives mandating certain changes be made to aircraft during their service life so that the aircraft can stay airworthy.  The paperwork for these ADs is part of the aircraft logs, and thus stays with the aircraft for the life of the aircraft.
However, just because an AD is marked as complete and closed out in the paperwork does not necessarily mean it has actually been completed.  This was a causative factor in the Omega flight 70 mishap, where an engine fell off a 707 shortly after rotation and damaged the plane to the point where it could not climb out.  The investigation revealed that although the applicable ADs were marked complete, the upgraded part required to be installed to close the ADs out had not been installed on the mishap aircraft.  Instead, a prior owner had marked the AD at the time complete when it had not actually been fully closed out.
How can an aircraft owner ensure that the ADs that the paperwork says have been closed out on an aircraft have actually been closed out and not simply pencil-whipped?  Are such verifications ever performed during maintenance or inspections (including pre-/post-sale inspection), or is the paperwork trusted absolutely?  Furthermore, how can an inspecting mechanic accurately determine the completion status of ADs?  (For the 707 AD in question in the Omega 70 mishap, this could be done with a small template and some mechanic time inside the pylon, but I suspect some ADs aren't that easy...)

Usually this is done by mechanics during the annual or other mandatory periodic maintenance.

It's called "pencil whipping" and it is very common. Most of the cases are owner-driven in that a certain class of owner actually seeks out a cash-for-signature sort of arrangement. This is why pre-buy inspections from competent mechanics are critical.  Physical validation usually happens during annual but there are some ADs that are impossible to validate.

@acpilot -- would an airliner receive similar validation pre-buy by the buyer's mechanics, or during C/D checks for that matter?

The doc review for a large jet purchase is crazy.  They do inspections as well but I'm not sure how detailed they get.

For small GA aircraft you can check for AD compliance by noting whether there are receipts for the replacement part. e.g. defective parts and/or incorrect parts installed. Others, are fairly simple to verify e.g. checking that a transponder has the latest software version, verifying that a carb inlet hose was installed—not scat tubing. Some are just about impossible to verify without re-doing the AD inspection. e.g remove the fuel tanks and inspect the wing spar, remove and inspect the turnbuckles on the elevator cables. Mostly though, you have to trust the A&Ps who did the work.

The simple answer to this question will be yes, documented AD compliance will sometimes be verified by physical inspection. For example, I have done this myself by inspecting to ensure that AD 82-07-02 had been properly complied with on a C172 I was inspecting for the first time.

I can only speak for commercial aviation, but in my experience, we generally have 100% RII buyback on initial AD compliance issues. For example, if we have to run a new wire bundle or reroute a wire bundle as part of an AD, it has to be "bought off" by either a QC inspector or an RII-qualified mechanic. In these situations, I would say that the work is done properly 99% of the time. Rarely would someone put their name on something that's done incorrectly if they don't have to go back and do the work themselves. The response is generally "Call me when you get it right."
Where I think the FAA severely lacks oversight, in my opinion, is future compliance in upholding the standards of the AD. On the initial AD, you're not allowed to deviate one iota from the original without a very special process put in place. But what happens when you deviate 10, 15, or 20 years down the road?
Hypothetical scenario: An AD is written to reroute a wire bundle from other wire bundles because of some safety issue. The AD is complied with and life goes on. Twenty years later, a mechanic disassembles all the wiring in the area for "X" maintenance issue. He turns it over to the next shift to reassemble it. Next shift has no idea how it goes back together. It's not marked as AD wiring. There are no instructions on how it all goes back together (save for the AD paperwork from 20 years ago), so the mechanics put it back together per the standard wiring practices manual. They bundle and clamp. Bundle and clamp. They do a beautiful job, but guess what? It violates the purpose of the AD from 20 years prior. Do you think the FAA follows up on that? Nope. The company? Nah. They have paperwork showing the AD is complied with. So it's up to each mechanic to determine if what they're working on is part of an AD (even one from 20 years ago), despite no special labeling or instructions, and maintain that AD compliance. As we mechanics joke, "It'll all come out in the investigation."
My experience is that as time goes by, the integrity of many AD's slowly dissolves. That being said, if we as A&P's even smell the faintest whiff of an AD, our antennae perk up and we are very careful to maintain that compliance. AD  violations are the surest way to get a nice letter in the mail from Mr. FAA.

What's RII stand for?


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How are further structural failures prevented if an aft pressure bulkhead fails?
In a modern airliner, if the aft pressure bulkhead experiences a structural failure, what design features are incorporated into the empennage to prevent the empennage from being overpressurized (i.e. at or near cabin pressure vs the normal case, which is at or near outside pressure) to the point of structural failure?  Or, in other words, what keeps the next aft pressure bulkhead failure from blowing the vertical tail, or some other important part, off the airplane a la JAL123?

If what's escaping a compromised bulkhead is cabin pressure, not an explosion; the airframe structure aft of the pressure vessel is wide open for air to escape.  The structure is hollow from one component to the next with "lightening holes" wherever possible designed to minimize weight (nothing to do with thunderstorm lightning).  Additionally, the lightening holes provide for plumbing, wiring, maintenance, inspection access, and ventilation.
Unless there's an explosion or some catastrophic failure of the pressure vessel, escaping cabin pressure by itself cannot pressurize the open empennage.  Pressurized aircraft also have a safety valve to protect the pressure vessel from structural damage in the event of outflow valve failure.  The prospect of aft pressure bulkhead failure before other skin fracture is unlikely.
If you are able to peer in between the rudder and vertical stabilizer of an aircraft, you will likely see the openings.

So it wasn't the failure if the aft pressure bulkhead in JAL-123 that caused the nearly complete failure of that plane's empennage?

The APB was damaged from a tailstrike event.  The cause of JAL123 was attributed to improper repair of the APB and empennage following a tail strike.  Overpressurization was not the cause.

This from http://lessonslearned.faa.gov/ll_main.cfm?TabID=4&LLID=16&LLTypeID=2 "The internal overpressure caused structural failures in critical fin support structure, causing it to rupture and depart the airplane."

The cabin was not over pressurized.  The repairs to the APB and tailcone did not meet design criteria.  The word "failure" here is used loosely to describe a sequence of events.  Had the repairs and parts met design criteria and a rupture occurred, then there was a failure in respect to the part.  What failed in this case was a repair process.

@STWilson -- the cabin was indeed at normal pressure -- the APB failed, which overpressurized the empennage relative to outside pressure and caused the ensuing vertical tail failure

I would characterize this episode as an explosion due to the sudden rupture/ collapse of the aft pressure bulkhead.  I caution using the term failure as the APB was determined to be deficient beforehand.  It's not possible for aircraft structure to contain a blast.

source: Stack Exchange

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Why is TO/GA button disabled in 777 with weight on wheels or below 2 ft RA?
Recently a final report for accident of an Emirates B777-300 at Dubai on 3rd August 2016 was published. An important factor there was that when the pilot tried to recover from long landing by going around, the TO/GA buttons were inhibited because the wheels were on the ground and the pilots did not realize this.
Now at first sight, this seems like an unnecessary complication of the auto-thrust system that just adds a point the pilots need to learn. But I suppose the engineers did have some reason to add this bit of logic.
So what dangerous condition is inhibiting the TO/GA button when weight on wheels or radio altitude below 2 feet for 3 seconds supposed to prevent?
I would understand after reversers deployed, but before that going around is considered appropriate solution for long landings and bounces, both of which might trigger the inhibition.

I feel like a helpful clarification is whether the 777 has an auto-takeoff, or if it is assumed that only a human will control the plane when it's on the ground (auto-land excluded).

@zymhan, I believe it uses the TO/GA button on take-off, but it does different action as take-off thrust is determined differently than go-around thrust.

The TOGA button is not inhibited, but the autothrottle disconnects exactly for the reasons mentioned above.
if you push TOGA, the FD will still direct you for a go-around position of the aircraft nose, if you have the correct velocity of course..
What happened there was that they pushed toga, and because they still had enough speed- the FD directed them to pull, leading to a bleed of speed which led eventually to a stall and belly landing.

@StavNemirovsky, but doesn't the TOGA button engage the A/T if armed in other cases—on take-off and if it was turned off on approach for some reason? Since it does not do this after touch-down, it is still inhibited in this sense.

@janhudec the TOGA engages the take off/ go atound mode. This includes FD instructions and the Autothrottle. After landing  the button still works, but it does not re-engage the AT. From here on- ir's only semantics. Yo can ssy that AT engagement by the TOGA button after touchdown is inhibited, that would be more correct. Refer to the 777 FCOM for more.

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Why use Mach number for describing the speed of aircraft?
What does Mach speed mean for describing aircraft speed if the speed of sound changes with temperature?

The aerodynamics change with Mach number.
At low Mach numbers (< ~0.3) , air is considered incompressible; it has constant density along the stream line.
At higher Mach numbers, air is no longer incompressible; the density changes as the air passes over the aircraft. The compressing and expanding of air changes the way the air flows, and consequently it changes the performance of the aircraft.
At Mach numbers approaching 1, parts of the flow around the aircraft may breach the sound barrier. This leads to trans-sonic effects such a shock waves which affects the performance of the aircraft even more.
For subsonic aircraft the maximum speed is typically expressed by two numbers: the maximum calibrated airspeed and the maximum Mach number. The first is related to the dynamic pressure the flow of air creates and is typically the limiting factor at lower altitudes. The Mach number is related to trans-sonic effects and is typically the limiting factor at higher altitudes where are is colder and the speed of sound is lower.
For the pilot it thus important to know both the airspeed and the Mach number.

It may help to get rid of the notion that "speed of sound" has anything to do with actual sound, and think of it more as "the speed of (shock) waves in air", and I believe it will be easier to see why it is important to know how fast you are in comparison to how fast (shock) waves propagate. The sonic boom is essentially when the speed of the airplane is the same as the speed of waves, which means that the shocks the airplane creates travel at the same speed as the airplane itself, so it will create shocks on top of the shocks and thus adding up the intensity of those shocks.

It is easy to imagine that creating those booms / shocks  wreaks all sorts of havoc with the aerodynamics of the plane, and thus knowing how fast you are relative to how fast disturbances of the air move, is crucial. As mentioned in the answer, you can have supersonic airflow over just parts of the airplane even while the airplane is still slightly sub-sonic.

Because the Mach number is a local property of air. For flying the properties of the surrounding air are relevant, not the properties of the standard atmosphere.

Mach number is also used by ATC to apply separation standards between aircraft. If both aircraft are flying at a constant Mach speed, their separation will remain constant.

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What are the approximate glide angles for modern passenger jets?
What is a typical glide angle for a modern passenger jet with engines idling, with full flaps and with the gear down?

Related: How does the Boeing 787 Dreamliner's glide ratio compare to other airliners?

Slightly related Why is a 3 degree descent angle used?

It must be in the region between 1/5 (11.3°) and 1/10 (5.7°), and closer to the shallower angle. I guess you want the value at 1.3 times stall speed - without a speed an answer would be impossible.
Once the glide ratio drops below 1/5, the energy dissipation is too quick to allow rotation for a soft touchdown with idle thrust. On the other hand, a glide ratio much in excess of 1/10 will make the aircraft float along the runway in ground effect, which makes the precise selection of the touchdown point (at the correct touchdown speed) hard. Spoilers help to adjust the glide path angle to steeper values, so the aircraft with flaps and gear fully deployed but the spoilers in should have a glide angle around 5° to 7°.

The requirement to go around with OEI does not permit much worse than the 1/10. E.g. A320 (which IIRC can use full flaps even with OEI) has MLW 66 t and single engine thrust 98 kN (the least powerful variant). Out of that, 21 kN is needed to achieve 500 ft/min climb rate at 150 knots and what remains gives weight/thrust ~8.6.

Depends on the requirements of the approach.  A typical PAPI or ILS glidepath is 3.5°.  But some non precision as well as precision approaches are steeper.  The LOC/DME-E for KASE has a steep final approach angle of 6.59°.
Peter's assessment of glide angle is good as well, though one might be able to fly a little steeper with judicious use of power when entering the round out to arrest the descent.

Typical ILS/PAPI is 3.0, not 3.5.  That "E" approach is a circling approach, not a straight-in. The question specifies Full flaps, gear, and IDLE thrust, and in those conditions you won't be able to hold a 3 degree (nor even 3.5 degree) glideslope -- you'll bleed airspeed pretty quick with that much drag.  In a 737, idle/gear/flaps 40 probably gives about 5 or 6 degrees, depending on winds & weight -- plenty of capability to catch a glideslope from above.

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What is the formula for induced drag?
I am looking to create one of these graphs for a simple model I tested in a wind tunnel.

I have managed to define the lift coefficient and thus I've been able to create the parasitic drag line. The problem is that I am having issues with finding the correct formula to use for the induced drag. I have been looking a while now and the only formula's I have found had the induced drag increase with a higher velocity.
the problem i'm running into is that the formula i see around is
$D_i = \frac{L^2}{\frac{1}{2}\rho V^2   \pi b^2 \epsilon}$
this formula has Lift squared above the divider and lift itself is dependant on velocity so whenever I use that formula the graph I get is of one that increases with speed instead of decreases.
What I'm asking for is the correct formula to use here

I'm just totally "winging" it here, but isn't Lift also dependent on AoA, and constant for straight-and-level flight, regardless of speed? ie as V increases, you decrease AoA to keep L constant and the airplane in level flight?

Additionally, parasite drag doesn't depend on lift?? I may be totally off base, but it sounds like you may be super confused about terminology and baseline assumptions.

You may also read this: What is wing inductance? to get a definition of the coefficient of induced drag. You can use this coefficient the same way than $C_L$ for the lift.

The problem i'm having is that I want to make a graph for the induced drag. But whenever i use the given formula the drag increases with a higher speed instead of decreases since lift is also dependent of velocity. I just can't work out how to get the correct graph.

@Patrick why does the lift increases with speed? is your aircraft somehow gaining weight while it travels? or are you forgetting to decrease $\alpha$ (AoA) as Daniel said above?

Thanks for the help guys, I didn't know that for such a graph the lift should stay equal to the weight.

It seem your graph of induced lift is not decreasing because you assume that the lift increases with velocity. This is generally not the case.
Typically, a drag vs velocity graph is made for unaccelerated level flight. Under these conditions the lift is equal to the weight of the aircraft.
$L = W =  \frac{1}{2}\rho V^2 c_L S$
From this we can obtain the lift coefficient as a function of velocity:
$c_L =  \frac{W }{\frac{1}{2} \rho V^2 S}$
The drag of the  aircraft is the sum of the parasite drag and the induced drag:
$D = D_p + D_i$
With the parasite drag:
$D_p = c_{D,0}\frac{1}{2} \rho V^2 S $
And the induced drag:
$D_i = \frac{1}{2}\rho V^2 S \frac{c_L^2}{\pi  AR \epsilon} =
\frac{W^2}{\frac{1}{2}\rho V^2 S \pi AR \epsilon}  = \frac{W^2}{\frac{1}{2}\rho V^2   \pi b^2 \epsilon}$
It is important to understand that this only holds when the lift is equal to the weight of the aircraft (e.g. straight & level flight)
Nomenclature:
    $L\:\:\:\:\:$ lift
    $W\:\:\:$ aircraft's weight
    $\rho\:\:\:\:\:$ air density
    $V\:\:\:\:$ velocity
    $S\:\:\:\:$ wing surface area
    $c_L \:\:\:$ lift coefficient
    $c_{D0} \:$  zero-lift drag coefficient
    $\pi \:\:\:\:\:$  3.14159$\dots$
    $AR \:\:$  aspect ratio of the wing
    $\epsilon \:\:\:\:\:\:$  the wing's Oswald factor
    $b \:\:\:\:\:\:$  wing span

Thanks a lot for the answer, this should solve my problems and you probably saved my ass <3.

Dear @DeltaLima, I quoted this From this we can obtain the lift coefficient as a function of velocity, then the equation. CL =  W/(0.5rhoV^2S). I red many times saying that way. My question, should not the coefficient of lift is calculated in the wind tunnel test? How can we calculate coefficient of lift while we still don't have Lift force? The Coefficient of lift itself we require is to calculate the lift, not vice versa.

@AirCraftLover In this case, we know the lift force. When the aircraft is in horizontal, non-accelerated flight (i.e. no turns); the lift force is equal to the weight of the aircraft. So the lift coefficient follows from the weight, speed, air density and wing surface area.


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What is the definition of “blade scatter” in gas turbine compressor dynamic balancing?
Can someone help me define “blade scatter” gas turbine compressor dynamic balancing?

What help do you need? Is there something about an existing definition you don't understand?

I cant’t find the definition of “blade scatter

Do you have any context for this term?  Where/how is it being used?

Sorry for incomplete information. Actually I’m looking for phenomenon called “blade scatter” during dynamic balancing.
And it is due to what? Thanks

I’m guessing slightly here but I know that at least some turbines allow the blades to shift slightly around the axis of rotation, allowing the turbine to self-balance to some degree, particularly in a case where a blade parts company but also in normal operation.

I assume there is an ellipsis somewhere in your source text, meaning the intended interpretation is "blade weight scatter", which does make sense in the context of dynamic balancing.
The meaning should be self-explanatory: the distribution of weights among nominally-equal turbo-machinery blades, which is important to keep the inertia tensor of the assembly as diagonal as possible when using the usual axis.

Maybe "blade scatter" refers to this

Bladed disks that allow for thermal expansion of blades at the root will allow the blades to "seat" themselves differently from run-to-run on the balancing machine. This causes the unbalance condition to vary slightly from balancing run to balancing run.
To reduce the effects of blade scatter, one typically takes multiple measurements and averages them together prior to making a correction.


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How is the FPA (flight-path-angle) computed?
How is FPA computed by the Auto-pilot to follow the  desired FPA? One part is clearly VS, is the other part IAS or Ground speed? Where does Ground speed come from?

The flight path is a path defined with respect to the ground. Therefore, the flight path angle must be computed with the ground speed:

The flight path angle $\alpha$ is calculated by the on-board computers with:
$$ \alpha = \text{arctan} \left( \frac{V/S}{\text{GS}} \right) $$
The source of the ground speed would in general be aircraft dependent, but for an airliner this would come from the Air Data Inertial Reference System (ADIRS). See also How is the actual ground speed of an airliner measured?
Some non-precision approach charts will also have a table with required vertical speeds for various ground speeds to maintain the target flight path angle. This is particularly helpful if your aircraft cannot fly a given FPA itself. This is an example from Amsterdam Schiphol (EHAM) VOR Approach for runway 09:

If you e.g. fly with a ground speed of 150kt on this approach, you would just dial in 800ft/min and you would get the desired 3° FPA.


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How to best navigate around and land at KPAO (Palo Alto, CA)?
Flying VFR into KPAO from the South for the first time in a Cherokee. Any advice on the best way to navigate KSJC and the SFO Bravo?  Thanks.

I asked a meta question about this

If you’re coming in VFR from the south, I’d recommend skirting around the San Jose Class C and Moffet’s Class D by flying over the Lexington Reservoir, over Los Gatos and Saratoga and staying just north of the foothills of Palo Alto.  Flown at lower altitudes, you’ll avoid KSFO’s Class B airspace.  Just be aware there’s a lot of GA VFR traffic down in the weeds in that area.  Also be aware of TFRs over Stanford, should they be hosting football games at their stadium.   Typically arrivals and departures from the west are given the Stadium visual arrivals, routing them to Stanford Stadium, thence to a downwind or base entry at KPAO.  Arrivals and departures to the north are given the Bridge visual arrival and departure to the Dumbarton Bridge then entry into KPAO pattern.  Remember as well that “Kung Pao” only has a 2400 ft runway, so be on the ball with you short field ops.  There is extensive flight training going on at that airport and the pattern can be extremely busy on good weather days.  Have a taxi diagram ready to go and be aware of taxi routing via the east loop Taxiway Golf - terminal side - or the west loop taxiway Golf - hanger side.


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Do airports have their own incident/accident investigation departments?
Do airports have their own incident/accident investigation departments? or they are restricted to the NCAA/Safety department only?

Welcome to aviation.SE! I don't completely understand your question, are you asking if airport authorities participate in accident investigations?

In the U.S. an airport will have safety teams and internal incident/accident reporting. This is more for airport operations and OSHA standards. It has little to nothing to do with what we typically think of FAA/NTSB incident and accident reporting and investigation. The airport’s team is strictly internal. Although, it may have to report to some external entity if safety laws and regulations were broken. Or, they may have some reporting obligations if Human Resource or labor laws were broken. All of this has more to do with the airport having to operate like any other large business or government entity.
The NTSB/FAA can, however, request at their discretion that an airport or its authorities participate in the federal incident/accident investigation.

More often than not, the accident investigation boards in Europe are a governmental unit independent of NCAA. The Board should be able to criticize and put requirements on all units involved in an accident/incident. This obviously include the CAA.
Departements and organizations are free to do an accident investigation. Availability to an accident site may be limited, though.
E.g. IFALPA have a structure of their own Accredited Accident Investigator, available for any relevant investigations.

Thank you Mr.Ursus for your explain.I wanted to know that should the airport direct has it's own Inc/Acc investigation board? or it's not mandatory?


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Torque and engine torque after aplying prandtl tip loss factor
I have a question regards to the following formula related to Blade Element Momentum theory for the application to calculate on airplane propellers:
$$    dQ=4\pi r^3 \rho V_\infty(1+a) a' \Omega F dr $$
where

$Q$ = angular momentum
$r$ = radius
$V_\infty$ = aircraft's forward velocity
$a$ = axial inflow factor
$a'$= angular inflow factor (swirl factor)
$\Omega$ = angular velocity $\left(\frac{2\pi n}{60}\right)$
$n$ = rotations per minute
$F$ = prandtl tip loss factor

As a result of using the tip loss factor which are numbers between 0 and 1 the end result of the calculated torque Q is lower.
I have sincere trouble understanding what this means.
Either the propeller runs with less resistance meaning that the propeller will run faster (higher rpm's) while keeping the engine power constant.
(Shaft torque is equal)
Or
There is a loss in torque which means the engine has to deliver a higher torque and so the propeller runs slower (rpm's go down) while keeping the engine power constant.
(Shaft torque is then not equal)
Which is the case?
If it is the latter, then how is the torque calculated that the engine needs to be able to deliver?
In case of a wind turbine I somehow find this much easier to understand. There is a certain amount of power delivered by the wind. After the tip loss correction has been applied the resulting Q can directly be used to calculate the expected power output.

Do you have a source for that equation?

http://www.aerodynamics4students.com/propulsion/blade-element-propeller-theory.php
https://en.wikipedia.org/wiki/Blade_element_momentum_theory
http://www.icas.org/ICAS_ARCHIVE/ICAS2010/PAPERS/434.PDF

You answered your own question by describing the effect of tip losses on the power output of the wind turbine.
But, like so many, the "tender trap" is getting stuck on the notion that somehow, engine "power" is constant.
Using pure logic, tip losses work both ways: affecting power from the airflow to drive a generator, or from the engine to move air.
So, when calculating torque required from the engine without tip loss factor, and comparing to calculations with tip factor, it becomes apparent that more torque must be applied, resulting in a higher RPM, to generate the desired thrust$^1$.
How to increase RPM?

Step on the gas (increase throttle)!

Torque is Newton-meters.  The pistons give Newtons, the radius of the crankshaft is meters.  Increased RPM is the result of the higher torque of the motor, and the drag of the propeller, finding a new equilibrium angular velocity.

What does this all mean?

Just as, theoretically, stronger wind is needed to generate the same power with tip losses, more fuel is needed to generate the same power with tip losses.  (one reason why modern windmills are very high aspect ratio).
So when calculating Thrust Specific Fuel Consumption, expect a loss of efficiency, $\eta$, due to tip losses.
$^1$ or ... prop AoA can be increased.

Thanks this is great info. Keeping the engine power constant is what I do in my calculation model. I've done what you suggested, instead keeping the thrust constant. Indeed model shows increase in needed power and decrease in efficiency. So I guess the model is correct after all. I did expect a higher impact from correction factor though. With this prop approx 2% increase in needed power. It's just so confusing that Q increases when I keep the engine power constant, although thrust and efficiency are going down as well indeed.

As a result of using the tip loss factor... torque Q is lower. I have sincere trouble understanding what this means.

The effect of the tip loss factor is to model the more or less sudden drop in lift which happens close to the tip of the blade (picture taken from this answer):

So, being all the other parameters the same, including the tip loss factor in the calculations will result in less torque and less thrust too, exactly because the tip loss factor models this reduced lift at the blade's tip.
To compensate for this reduction and to get the same total thrust, pitch needs to be incremented with the relevant even higher increment of drag and therefore of needed torque. Obviously higher pitch also implies being closer to stall conditions. In general a higher number of blades (at constant solidity and disk loading) smooths out this effect.


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Are airliners' pilots trained to safely ditch an aircraft?
After reading this question and these two answers it is clear that ditching is taken into account, at least for biggest airliners (and with reasons as it occured several times in aviation history).
Pilots are trained to face many technical problems that may lead to an accident (engine flame-out, cabin fire, partial loss of hydraulic power, partial loss of flight computers,...).
But, many airlines pilots do not posses the qualification (nor the training) to pilot specific categories of aircraft such as fighters, gliders or seaplanes. Thus it makes sense to assume they are not trained to fly in formation or land on water.
Is an airliners' pilot trained to ditch as he is trained to deal with technical emergencies? If not, what is its knowledge of such situation (only theorical, practice once on simulator,...)? Is there differences between country's regulation?

This is a very dated answer now, but for what it's worth, prior to my retirement in 1999 from a U.S. airline, we did ditching scenarios in 747-100/200 sims during initial training and then occasionally during recurrent training. Proper execution included being on-speed for your weight, nose attitude at touchdown (5 degrees up as I remember), aircraft configuration (gear up but I don't remember the flap setting), determination of wave direction if possible, and landing parallel to the wave action. It was a relatively easy scenario for the pilots but a busy scenario for the flight engineer. He had to position valves properly at the right time, including making sure the pressurization outflow valves were closed to prevent fuselage flooding.

Wouldn't fuselage damage cause the plane to flood anyways, no matter whether the outflow valves were open or closed?

@I have no definitive answer for that, but my guess is that the fuselage damage would vary greatly depending on the circumstances of the ditching, especially wave action and whether you were successful in landing parallel to the waves. Also, at least so were we told as I remember, even if the fuselage is compromised, the wings can provide flotation for a time assuming they stay attached. Even with fuel in them they can be expected float given that fuel weighs less than water: something like 6.7 lbs/gal for fuel, 8.4 or so for water as I remember.

There is underwater pilot survival training, but its mostly for small planes and for helis:
http://www.proaviation.ca/Egress.html


text:
Why are safety demonstrations done while taxiing?
In airliners, safety demonstrations are performed when the aircraft is leaving the gate. I understand it cannot be done latter as an aircraft incident including an evacuation may occur at take off roll. But I think it could be done earlier (e.g. in waiting area before boarding). This way, if any passenger has any question (e.g. this one), this passenger has plenty of time to ask flight attendants before takeoff. This time may also be used to explain why safety demonstration include all those items (life vest inflated outside the airplane is not the only item that could raise questions). Moreover it could be a good use of waiting time before boarding.
EDIT: As highlighted by one answer, some airliners use video to do this demonstration. In this case, the generic items (i.e. not aircraft specific) of the video could be played on screen in waiting area in addition to the actual briefing.

If push back is delayed and everyone is on the plane they will go ahead and do the safety briefing.

Some might describe standing up in a long corridor of a moving vehicle a safety concern. So it's rather ironic that this is how a safety demonstration is conducted.

Pointing out the exits wouldn't work so well in the terminal.

One thing missed in the answers so far.  I count the seat backs between me and the exits in front and behind.  That way, no matter what, I can count them as I move towards whichever exit I might need to use.

@Dave "Some might describe standing up in a long corridor of a moving vehicle a safety concern." Tell that to anybody who commutes by train or even by bus. Heck, tell that to the passengers who just used the airport monorail system to get to their gate. Standing on moving vehicles is a societally accepted risk.

Yes, please: Let's have more random noise in the waiting area!

@Dave Have you ever responded to a bus crash? It's not pretty, and there are some very clear and obvious reasons as to why. So yes, it is a safety concern, and a potentially lethal one at that. Whether we are forced to, or socially accept it or not.

A very simple answer to this question is that the FAA (and international agencies) require it to be so to ensure that all passengers are available to hear/see the briefing.
The other more robotic/pilot-like answer to this is because it is on the taxi checklist. Haha :)

Many passengers don't reach the gate until seconds before the gate closes for a variety of reasons. They won't get the pre-boarding briefing.
Taxiing is the only time before takeoff where the crew knows for sure that all passengers that will be on the plane are there.

also, the moment the aircraft begin taxing, you're sure every passenger is seated and not busy (e.g. stowing carry-on baggage on the overhead bin or under the seat, etc.)

The passengers aren't the only thing that might change: in some (albeit rare) circumstances, the plane might also change at the last minute too. Imagine a briefing that said "Seats 12 and under will go forward in the event of an emergency, with the rest going to the back" only to find in this plane it's from 15 instead.

The waiting area is a poor choice of place to give a safety briefing. Passengers are talking amongst themselves, fiddling about with hand luggage, or listening to music on earphones, and may not respond well to being interrupted for the briefing. There are often disturbances (e.g. passengers on other flights passing the gate). As ratchet freak pointed out, not all the passengers will arrive early, and if everything is running to schedule, there shouldn't be a wait between the announced boarding time and the actual boarding.
Typically, before boarding (most of) the cabin crew is on the aircraft getting ready for the boarding. They don't have spare time to go to the gate to perform the demonstration, so it would mean having extra staff who just do briefings, with an extra risk of briefing for the wrong aircraft. In addition, it's only possible to point out the overhead panels and emergency exits when you're in the aircraft.
On the aircraft immediately before take-off, every passenger is in their seat, with no headphones in (in case of an emergency), and the cabin crew are spread out with nothing else to do. It can be an anxious time for passengers and crew alike. It's not only a suitable free period: the briefing makes an important activity to keep passengers and cabin crew alike busy during this time. Finally, even if passengers don't listen to the briefing, it gives them a minute to picture the exit routes in relation to their actual seat location, and mentally plan for an emergency.

You can also include that safety instructions take into account the aircraft type, so the cabin crew or other ground personnel cannot give a standardized instruction, but must give one relevant to the aircraft.

You also can't point at things in the aircraft if you aren't in it. And for airlines without reserved seats people may not know where in the aircraft they will be sitting until they sit down.

This simplest answer is a matter of economy. If the airline gave the briefing in the terminal or wherever before loading the passengers, then the airline would have to allocate resources (personnel, demo gear, logistical planning, and policies) to preform this task. It could be done but the cost (monetary and intrinsic) would be high and the ROI would be little to none.
Instead, they choose to do it while taxiing because it is the most economical time to do so as the flight attendants have little to do (as opposed to during flight where passengers are unpredictable in their needs).
Also, interesting to note is how some flights (Delta at least) have switched to a fully automated system for the safety briefings. Note that this procedure actually saves money by freeing up resources previously committed (as well as potential ad revenue).

Most of the airlines I've traveled on recently that have in-flight entertainment systems use a video for the briefing. Delta still does it manually on most aircraft without IFE systems, though some have audio recordings. But, yes, that is a good way to ensure that nothing is inadvertently skipped and also relieves the FAs to do other stuff. It's also pretty common for airlines to make these amusing in order to try to make it more likely that passengers will actually pay attention. Air New Zealand is particularly well-known for this.

If fully automated, the safety video could also be played on screens in waiting area

@ManuH Where an even larger proportion of the passengers will completely ignore it or be unable to properly see a screen.

In what sense is there "potential ad revenue" from giving the safety briefing on the in-flight entertainment system?

@DavidRicherby it could be done in addition to safety demonstration

@ManuH If you're still going to do it on the plane, there seems to be little benefit to doing it at the gate as well.

@DavidRicherby OK. I have another question. Stiil, repetition is a good way to learn something.

@ManuH, if played in the waiting area, there would have to be a policy in place to ensure that all passengers watch it. Once again, what is the financial benefit to this?

@DavidRicherby, the potential ad revenue could come in at least 3 forms: (1) increased rapport/competitive edge among competitor airlines -take reirab's referral of Air New Zealand as proof, (2) direct product placement -I have no proof that airlines are doing this but potentially, they could offer to display a 'coke' instead of a 'pepsi' product for instance, and (3) the direct upsell of airline specific services -for instance, a brief loyalty program reference while you are already listening can be highly effective in subconscious advertising.

@MatthewPeters Your point (1) has nothing to do with ad revenue: it's about using a well-crafted safety announcement to increase brand exposure. Your points (2) and (3) havennothing to do with safety briefings: I've never seen soft drinks or loyalty programmes mentioned in a safety briefing, because they have nothing to do with safety. So, I ask again: in what sense is there "potential ad revenue" from giving the safety briefing on the in-flight entertainment system.

@DavidRicherby, because advertising is defined (at least in my mind) as in promoting [with the intention on increasing sales], I would argue that my three major points promote and potentially increase sales. The effects are no doubt subtle but when dealing with a macro system such as an airline serving millions of passengers a year any micro system concern (ie from the passenger's reference) will seem irrelevant. Research a little more into marketing and in particular subtle and subconscious decision making to learn more.

@MatthewPeters I have twice directly asked you for a connection between safety information videos and increased ad revenue. You have given such a connection on neither occasion. I'm forced to conclude that you can't think of one.

While the above are certainly good reasons how this came to be, today the answer is very simple and is the same for almost all commercial aviation questions starting with "why": because there is an FAA regulation and changing an FAA regulation needs monumental effort and thus needs an extremely compelling reason first.


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What would prevent a solar powered aircraft staying aloft forever?
Focusing on aircraft, not balloons, I found this question that led me to some basic research on atmospheric satellites. I imagine the technology has evolved since NASA's research more than 10 years ago.
Given the following points:

The aircraft cannot stay in flight forever, as it must land for maintenance (as would any aircraft).
In 2001, NASA planned a 40h long trip based on solar powered technology.
A fuel-powered UAV can stay up to 33h in flight.
The Qinetiq Zephyr stayed aloft about 2 weeks.
Redundancy can be added to continue operation in case of equipment failure (as in any commercial aircraft).
'Real' satellite can stay airborne for several years (payloads seem to be able to operate several years without maintenance)
If the aircraft can land, the payload and equipment do not have to be as reliable as they would on 'real' satellites, as they could be changed or repaired.

For an atmospheric satellite based on solar-powered airplane technology such as the NASA's Helios, operated in normal conditions, what is the most restrictive element that make landing compulsory?

Probably because there is no application that needs that, why to create an overdesigned airplane?

Although it isn't an exact match, this question covers a lot of relevant points

Related, if not an outright duplicate: What are the factors limiting how long an aircraft can stay aloft? - All of these (including  fuel: availability of sunlight / battery capacity) would apply to a solar aircraft.

Balloons can stay aloft indefinitely. But they don't because there's really no need to

I believe that currently, even being at the very frontier of pholtovoltaics and battery technology, those things simply have barely enough power to lift their batteries off the ground, let alone carry some substantial payload. We would either need a significant breakthrough in battery technology (storing much more energy per mass) or photovoltaics (much more efficient solar cells reducing the need for batteries). Breakthroughs in material science (lighter materials) probably won't help much, since the weight is dominated by the batteries anyway. Although, more resilient airframes may help.

The most common failures in planes start with: a human mistake or a mechanical failure. Where, of course, mechanical failures are much more likely to happen on moving parts.
Satellites have very little moving parts: you get couple servo motors to adjust the angle of your equipment such as the solar panels and the antennas. Both happen in units of full rotations a day. You also often have some small rocket engines to correct the satellites course, but they are rocket engines whose moving parts comprise more or less just one valve.
In a plane, however, you have pieces that move very fast and fluids of all kinds (not only fuel which you need not have on a solar-powered plane, but also lubricants, hydraulics etc.), also very sensitive mechanical sensors whose non-stop operation is crucial for the flight. This all needs to be inspected, oil levels checked, hydraulics checked. Last but not least, the weather in the space is quite calm, compared to the atmosphere. Depending on how high you fly, you meet clouds, storms, birds, temperature changes etc., which all can add to the wear of things and make things require maintenance.
I'm not sure which would be the limiting factor, but I think that either some equipment wouldn't be operational without maintenance, or you would get a mechanical failure of some kind.

Considering Helios flies around at 96,000 feet, clouds and storms usually aren't an issue. Also, birds tend to stay a bit lower than that...

@reirab Yes, I know, but these were minor points in my answer, and after all, you still get weather and winds up there, just not as violent.

Other than mechanical or human factors, the other key considerations would be the weather and the season.
The weather would affect even a high-flying solar powered aircraft because they descend (albeit slowly) during the night cycle.  In addition, their design requires a very carefully managed flight envelope: an unstable air mass could easily destroy the aircraft. Note that thunderstorms, jetstreams and even mountain wave can reach into daytime flying heights as well.  There needs to be a trade off between how high the aircraft can fly in the thin air and the size, weight and fragility of the resultant design.  This would put the aircraft at eventual risk during one or more phases of the flight.
The season (in combination with the aircraft's position) would affect the amount of energy it could receive from the sun.  Whilst a solar powered UAV may fare well in the summer months in the northern hemisphere, it may not be possible to fly it continuously in the winter months, for example.  As most applications are location specific, and typically over industrialised regions, this precludes moving the aircraft to the equator or flying a sinusoidal pattern between the two tropical circles.
In your mechanical assumptions it would also be worth accounting for ionising solar radiation (which may affect onboard computer and memory chips) and stronger UV light, which is likely to have a degrading effect on most of the materials used to build the aircraft.
Finally, just a mention that redundancy may be a sensible approach for when there is spare payload and/or energy, but would be less desirable when these were both at a premium.

One that I can think of is the charge/ discharge effectiveness of the battery. the more charge/ discharge cycle applied to a battery, the less effective the battery can hold its charge, down to 70%. Eventually, the batteries need to be replaced before running out of power at night.

There are some practical matters which factor into this issue.
With satellites there is a high launch cost, and servicing them in space is also very expensive.  So the systems are designed for an economic life which is derived from the expected failure rates of all the systems, and things like the depletion rates of RCS used for station keeping, etc.  So there is a high economic incentive to design systems that have a long life.
With solar powered UAS, the costs are much lower, and certainly the launch cost is a couple of magnitudes or so less. The cost to service is low, if the aircraft can be retrieved, maintained and relaunched. So really there is little economic incentive to make the investment to have a UAS which can stay on station for years.
So in my opinion, it is possible to have solar powered UAS which will station keep for very long times, but there is little economic incentive to develop the high reliability systems (perhaps including redundancy) because the cost to retrieve and relaunch is low.
One such application for aircraft like this is to provide data connectivity over cities or even remote areas, kind of like launching an airborne hotspot.


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What are the differences in design considerations for ground attack and air dominance aircraft?
What parameters and types of performance are designers trying to maximize when building an air dominance fighter plane rather than a ground support fighter? What are the trade offs between them - what do I sacrifice to make a great fighter aircraft vs. a great ground support aircraft?

One thing to note is that 'pure' air dominance fighter or ground attack aircraft is not being developed anymore. Most of the combat aircraft developed recently/under development are multirole (or 'omnirole') aircraft.
In case of air dominance (or air superiority) fighters, which have the task of eliminating enemy air defense system especially fighters and securing aerial control for operation of friendly forces without harassment, the following are important design objectives:

High thrust to weight ratio, as it helps in maneuvers.
Stealth, as the enemy can't shoot what he/she can't see.
High maneuverability, for close combat situations and evasion.
High weapons load, as it enables engagement of a large number of enemy aircraft at once.
A good range, as it is better to engage enemy aircraft in their area rather than in friendly territory.
A powerful radar to track and engage enemy aircraft, as it enables them to shoot first.
Communication links to transfer data between the aircraft and between the AEWACS aircraft, as most of the aircraft today operate in an integrated battlefield.
Speed is also a very important parameter.

In case of ground support (or attack) aircraft, whose primary task is the destruction of enemy logistics and/or support for ground troops under fire, the designers look for similar yet a bit different set of characteristics.

Ruggedness, as the aircraft should be able take some amount of punishment and return home.
High endurance and Time on Target, as the ground troops may require support for an extended period of time, with corresponding weapons load.
Communication links between aircraft and ground troops for obvious reasons.
Precision targeting systems for situations where friendlies are in close contact with the enemy troops.
Ability to operate from forward operating bases is desirable.

Most of the present generation aircraft carry out their ground support duties using precision weaponry rather than any fundamental design decisions. Though there are still trade-offs, as in any aircraft design.

The weapon load of stealth aircraft is lesser their non-stealthy counterparts as external weapons carriage increases the radar signature of the aircraft.
For ground attack aircraft, a high subsonic speed is more than enough unlike the supersonic air dominance fighters.
Low altitude maneuverability is important for ground attack aircraft for quick ingress and egress from the combat area.

One aspect of aircraft design is that combat aircraft optimized for high altitude operations can face higher stresses when operating in lower altitudes (i.e. near ground). For example, when USAF switched B-52s from high altitude bombing role to low altitude penetration tactics, it caused increased stress in the airframe.

The early design mission profile for what became the F-22 was ground attack - attacking Soviet airfields in Central Europe to grab air superiority from Day One onwards.

@DeerHunter in fiction, yes. In reality it was never a serious consideration (though it may have been mentioned off hand to some congresscritters that it could be done) to get them to fund the project. It was designed to be a pure air defense aircraft, like the F-15 was when created ("not a pound for air to ground" was the meme for the F-15). The idea was that the F-22 would provide top cover for swarms of ground attack aircraft.


text:
What are those trucks towing around, and why?
I was in Prague airport and saw those things going around:

As for title, what are they towing and why? I can imagine it could be to alter airport layout, but I don't see a use for it.
Sub question for and additional answer's virtual bonus: is it funny as it seems? I could imagine drifting those things around :-D

They are called "Jersey barriers" and are temporary barriers used to alter the layout and to introduce defined lanes for vehicles, passengers etc.
For the bonus, they are not fun to tow.  If that line starts snaking, you have to stop until they all settle down before moving off again. Try drifting with those, and the weight would get so far outside your turn radius in no time flat that you'll spin the vehicle and jack-knife the lot.

Border Barriers UK©

RentPlasticJerseyBarriers.com©

@J.Hougaard Good spot. That's worth an answer in my opinion.

As Simon pointed out, the cars in your image appear to be towing airport barriers, which are used to visually mark areas on the aerodrome that are temporarily not available for air traffic.
They are typically used during construction work on or near runways and taxiways at an aerodrome, like in this image:

Although air crews are notified of such construction work through other means, such as NOTAM's and information from the air traffic control, the visible barriers are there to add another level of safety to prevent traffic from entering such areas. There has been a number of incidents and accidents where aircraft have entered closed areas, in spite of the fact that information of the closures was published correctly. See more here: http://www.skybrary.aero/index.php/Runway/Taxiway_Construction_Risks
I do not know how recent your image is. If it is recent, it may very well be related to some of the below NOTAMs, which announce closures of different areas at Prague airport:
Q) LKAA/QMXLC/IV/M /A /000/999/5006N01416E A) LKPR B) 16/09/11 09:35 C) 16/09/11 13:00 E)
TAXILANE BTN TWY 'R' AND TWY 'P' CLSD. DAY MARKING
Q) LKAA/QMXLC/IV/NBO /A /000/999/5006N01416E
A) LKPR
B) 16/09/08 06:00 C) 16/09/30 12:00
E) TAXILANE FOR EXIT FROM STAND S55 AND S56 CLSD FOR ACFT TAXIING. DAY AND NIGHT MARKING.
Q) LKAA/QMXLC/IV/M /A /000/999/5006N01416E
A) LKPR
B) 16/09/08 06:00 C) 16/09/15 10:00
E) TWY R BTN TWY L AND ENTRY TO STAND S54 CLSD. TWY RR CLSD.DAY AND NIGHT MARKING

I don't know why you call those airport barriers. There doesn't appear to be anything airport-specific about them. I've seen them in many places, especially around roadworks on motorways.

@TRiG simply because I do not know the technical name for them :)

Although they might be identical, they cannot be called road barriers in this context.


text:
Is there any form of checklist that a pilot needs to go through before they use their ejection seat?
Obviously, the use of an ejection seat is a last resort tactic but is there anything at all that a pilot must consider, any buttons they need to hit or something similar before they may eject?
Obviously not including anything such as arming the ejection seat or removing any covers over the ejection seat handle or anything.

Pray hard!!!!!!

Yes there are checklists but a lot of the training is done by practice exercises so the procedure becomes instinctive during an emergency.
The exact procedures to be used vary based upon airframe, cockpit configuration, and ejection seat make and model.  Here are two examples, one from the F-16A/B aircraft and the other from the F/A-18E/F aircraft.
From the F-16 USAF Flight Manual.

And from the F-18 NATOPS Manual.

Again there are a lot of mitigating factors here, specifically, airspeed, altitude, attitude, aircraft controllability and imminent danger to the flight crew which must be taken into consideration to order to make the decision to eject.  Since an ejection seat is nothing more than a device to provide an additional velocity vector to the aircrew in order to provide time for the main parachute to open and safely lower the occupant to the ground, they have specific altitude, airspeed and attitude envelopes in which they may be operated to ensure maximum chance of aircrew survival.  This should be reviewed and thoroughly understood by the aircrew prior to use.

There have been a few instances where the seat was used outside of the envelope.  One notable instance being Soviet test pilot Anatoli Kobachev when he punched out of a MiG-29 during a low altitude, high AOA pass at the 1989 Paris Air Show.  His delay was to direct the stricken aircraft away from the crowds and very fortunate that he didn’t die.  He walked away from the accident.

The checklists above should be used only IF TIME AND WORKLOAD PERMIT.  Again flight crews practice ejection procedures separate from aircraft operation in order to become uncounsciously competent in the operation of the seat.  They typically order the cockpit and workstations for aircraft egress prior to situation where there is an increased probability of needing to abandon a disabled aircraft.  These include takeoff, landing, and entering a theater of combat, etc.  Checklists will be use here prior to these events and crews will probably brief ejection procedures here as well.  Carrier operations, in partcular will have crews ready to eject at a moments notice and anticipating emergencies such as a cold cat shot or arresting gear failure during launch and recovery operations, both of which will probably require an immediate ejection to save the lives of the aircrew.
Correct cockpit preflight procedures must be done by the aircrews prior to operations to ensure safe ejection as well.  Crew must attach the leg restraints as well as correct attachment of life support umbilicals such as oxygen, anti-G, radio and HMCS data lines to ensure they separate properly during ejection without causing serious injury or death.  Shoulder straps must be attached into the occupant’s parachute harness to connect them with the seat’s recovery parachute (some seats do not have this; the pilot will wear a separate parachute system as part of their life support garb in this case).  Charts, kneeboards and other foreign objects must be placed such that they do not interfere with the operation of the ejection handles or the seat safing handles.
The ejection process again is going to be based upon the cockpit configuration and seat type, but typically if the aircraft commander says EJECT! EJECT! EJECT!, you will pull your legs and extremities clear of the legwells and flight controls, head back against the seat headrest, grasp the ejection handles, disengaging the grip safeties and PULL HARD.  The ejection itself will happen fast and very violent with a BANG! BANG!  The canopies will either break away with a pyrotechnic charge or be fractured with a similar charge sounding like a shotgun blast at close range.  This is followed a split second later with a jolt and explosion as the pneumatic catapult throws you clear of the cockpit and the seat rocket motor ignites, giving you an approx. 20g acceleration clear of the cockpit.  After this, the recovery process becomes pretty automatic.  Air data sensors feeding a small computer in the seat right the occupant using a drogue chute, followed by seat frame separation and deployment of the main recovery parachute.  The pilot may be required th pull an additional handle for deployment of the seat pan and life raft for a water egress as well.
Wind blast will be a major factor and all material suggests that an ejection be intitiated at the lowest airspeed, if possible.  High speed ejections will invariably result in serious injuries as due to wind blast, as this chart from an F-16 flight ops manual suggests.

Ejection at supersonic speeds is usually fatal, with very few exceptions.  This pilot was very fortunate to survive a supersonic ejection, but was seriously injured in the process.

Great answer and great information. There really is an old 50's/60's/70's military instructional training video for everything.

Really, really worst case, grab the handle & pull.  In the T-37, the boldface checklist for ejection was, "Handgrips - Raise, Triggers - Squeeze" -- it was a 2-step process.  In the T-38, it was simpler, "Handgrips - Raise".
With a couple extra seconds, the drill was to get into a good tight body position with the helmet back against the headrest (looking straight ahead -- straight spine), feet tucked back against the seat, elbows in, hands on the handgrips, and then boom.
In the case when you had more time there was a "controlled bailout checklist". That could come into play in situations like having one main gear stuck down & another stuck up, which is considered an "un-landable configuration" in the T-38, since you'd tumble shortly after touchdown.  That checklist had a few more steps to it, like taking off the checklist that was velcro-ed on your leg, take pens out of your pocket, tighten your chin strap & oxygen mask, go to the controlled bailout area (essentially someplace with no civilization close by for the jet to crash into, but terrain you could probably survive landing on), slow to some prescribed speed, throttles to idle, trim for your glide speed, assume the body position, and then "Handgrips Raise."
Oh, and tell ATC what you were about to go do... they can send a helo to pick you up much faster that way!

An additional benefit of using the controlled bailout checklist...https://en.wikipedia.org/wiki/Cornfield_Bomber

Yes:

If the aircraft has more than 1 crew, they should eject at different times, not together. PILOT COMMANDS NAVIGATOR TO EJECT. Only after the navigator has ejected, should the pilot eject.
It is bad to eject if the aircraft is upside down, so that should be avoided if possible.
The seat harness should be tight, as well as helmet and mask. If any of these are loose, bad things can happen.
Pilot must hold on tight to the ring with both hands. Do not eject with only one hand on the ring.

Re 2. Several seats allow ejection in inverted flight above 100-140 ft. So, with those, it may be suboptimal but not really really bad.

Re. 1.  Ejection seat systems typically take care of this by sequencing the seats with enough separation to keep the occupants safe.

Re 3. and 4.  "...bad things may happen."  If you're using the ejection seat at all, your day has already gone from bad to worse and beyond!

@RedGrittyBrick I didn't say it was "really really" bad. I said "it should be avoided if possible." which is standard guidance.

@RalphJ Maybe so, but there is no reason not to take manual steps to make sure that simultaneous ejection is not happening. Why risk your life by assuming that an automatic system will work when you don't have to?

@redgrittybrick it takes 3-5 seconds for a chute to fully deploy from a rocket chair.  So unless the jet is moving fast with a high rate of climb behind it, an inverted ejection at 100-150 feet would almost certainly be fatal.

The ACES II seat is a 0 - 0 seat, and from Wikipedia The minimal ejection altitude for ACES II seat in inverted flight is about 140 feet (43 m) above ground level at 150 KIAS. If you're below that, there's a good possibility you couldn't grab the handles before impact.


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What is the official term of a plane flying under another plane to avoid radar?
I was watching the news and, just now, learned that the Russians used a "trick" by flying a fighter plane under a cargo plane to Syria and successfully avoided radar detection for the fighter plane.
I wanted to learn more about this method (a Wiki article, for instance) but failed to find anything. So do the experts here know what this term is called, if there even is one?

possible duplicate of Could an aircraft 'hide' in the aircraft shadow of another aircraft without being detected or noticed?

Not a duplicate. The other answer is not about terminology.

This is not yet defined; invent one!

@BogdanWilli - pretty much all stuff has already been...

My copy of "EW 101: A First Course in Electronic Warfare" calls it "formation jamming".

Mind you, an operator of a radar with non-cooperative threat recognition capability will at least suspect something is wrong (although not from all aspects and ranges).

If two aircraft are flying one above the other, they are flying in stacked formation.

12 Aircraft stacked formation SOP of 303 Bombardment Group, from 303rdbg.com
Of course, it is about flying, with nothing said about radar deception. This technique was used in B-17 combat boxes in WWII, where aircraft squadrons were stacked at multiple altitudes. One advantage of this tight box like formations was that they presented the anti-aircraft gunners with smaller target.


text:
In a dogfight, can a pilot shoot down a parachute?
Forgive me if my question sounds more like a rule of engagement for aerial combat than aviation technique. I was wondering that is it ok, in a dogfight, for a victorious pilot to shoot a defeated pilot's parachute to kill him. Are there any records of this type of event?

That would be terrible if someone did shoot the pilot after he was ejected out of the aircraft. The reason this rule is out here is because the pilot can cause no harm if he is not in the jet.

You question is a question of rules of engagement. Shooting down a downed pilot in a dogfight is not only not OK, but also illegal.
According to Article 42 of Geneva Conventions,

No person parachuting from an aircraft in distress shall be made the object of attack during his descent.

Of course, war is war and this kind of attacks have been practiced by pilots of almost all air forces, though it should be noted that in most cases, this practice was specifically prohibited by their high commands.

That's specifically Article 42 of Additional Protocol 1, which was not part of the original 4 Geneva Conventions and has not been ratified by as many states. However, this specific provision appears to be customary international law as well.

Yes. Still the Conventions cover most of the international conflicts and I thought it would be appropriate to quote it here.

Yeah, I was just pointing it out to be more specific.

The wikipedia page on this subject is actually pretty good.

There are numerous recorded instances from the Second World War of pilots being killed after bailing out of their aircraft, this was very common particularly in the later war years.


text:
What are these lights above the panel in a Blue Angels cockpit?
I found the following picture on the Blue Angels Facebook page:

What is the purpose of the lights over the pilot's panel? (The two on the top are green)

It looks like an angle of attack indicator.  One for each wing, green amber and red.  I guess it's so that you can see it easily in peripheral vision without looking in.  I can't find any reference.  We need @RhinoDriver

@Simon If I understood you correctly, the two green-shining lights at the top are AoA-Indicators for the left and the right wing. Correct? Then what do the four lights at the bottom do?

Two green lights, left wing AoA OK, right wing AoA OK.  Two amber lights, left and right wing approaching stall or some critical angle.  Two red lights, stalled.

@Simon Unfortunately still doesn't answer for what the four lights at the bottom are used :/

Yes it does - the two at the top are green, the four at the bottom are 2x amber, 2x red (one amber for each wing, one red for each wing)

@Simon Now I understand. If you are completly sure, please add this as an answer.

I am not completely sure and my Google foo, usually very strong, has deserted me on this one. I've seen a similar indicator fitted to Phantoms (F4s) on a training squadron but that only had 3 lights. It did not distinguish between left and right.  This is fine for fighters who rarely do "aerobatics" but for the Blue Angels , who spend a lot of time on the edge of the control envelope, it makes sense. From what I can find, it's not standard fit on F18s so my guess (again) is that it's a Blue Angels specific mod.

@Simon I agree with you, thank you. I know for the swiss air force F/A-18, they don't have this build in.

I'm finding it a little weird why to give 6 mutually exclusive lights of "on[color]/off" when 2 of variable color would suffice. Especially in such obtrusive location limiting field of view.

@Simon I'm pretty sure it's not AoA - I haven't ever heard of it being displayed per wing, and that's a lot of device for something that they'd also have displayed on their HUD.

I did say guess work, but is does seem similar to an indicator like this which in turn is very similar to one that was fitted on Phantom FGR2s on a conversion unit.

@Simon This is the Angle of Attack Indicator. See the answer below, they are placed on the left side of the HUD.

I'm not absolutely sure but I think they are the indicators for the inverted fuel pump. From arcforums:

I finally spoke to a friend of mine who used to fly with the Blue Angels during the 2000/2001 show season. He said the lights on the glare shield were for the inverted pump indicator. The BA fly inverted longer than what is normally permitted for the Hornet so the Blue Angels aircraft are modified with a boost pump mounted to the top of the fuel tank. When they fly an inverted manuver for an extended period that pump is truned on, and while inverted fuel is pumped from the main tank to the feed tank. As fuel in the feed tanks is burned, the light would turns from green to yellow to red. When the light turns red it's time to roll back to a normal flight attitude.

So the three sets of lights should be for the tanks on both the wings.
I think this is the answer because the angle of attack indexers are found to the left of the HUD and look like this:

Also, it appears that they (aoa indexers) are found in carrier aircraft (for e.g. A-4 Skyhawk) as approaches are flown at a specified angle of attack rather than at particular airspeeds.
I believe that these lights are Blue angel specific mod as I'm not able to find them in any other versions.

I think you're right, and they may also include smoke monitoring. There's a simulation mod group that flies as Virtual Blue Angels in the LOMAC engine, and they've built a replica cockpit. There's no print; the lights are certainly not amber, but white, green, and red; there's a separate AoA gauge pasted to the left of the HUD; and they mention BA specific hacks like Inverted fuel system lights and Smoke lights; ARM and SMOKE is marked on the left set.

@egid At first I thought the were for smoke monitoring. However, there is only one smoke generator (on the left nozzle if I remember correctly), so I discounted that. Also I think (again guessing) that the smoke indicator is on the left of glare shield.

Right side of the HUD:
Top row of 2 lights on the right side is showing the inverted fuel system is armed.  Below that are the failure lights for that system.  To the right of that is when the inverted fuel pump system is active (for the Double Farvel).
Left side of the HUD:
Left side is a smoke button that arms the smoke system.  Then to the left is a smoke on indicator, and the far right is the inverted fuel pumps switch that turns that system on/off.
The lights have NOTHING to do with AOA.

Welcome to aviation.SE! The [tour] might be helpful if you're new to the site.

authors: ป๋อง คลาสสิคไทยแลนด์


text:
What is the difference between aviation "accident" and "incident"?
When I hear speaking about aviation crashes, sometimes I hear about "accidents" and other times about "incidents".
What distinguishes them? Is there an international standard that determines how aviation crashes are classified or is it based on national regulations?

There are indeed only two 'official' classifications of aviation incidents, which are defined in ICAO Annex 13.

Accident. An occurrence associated with the operation of an aircraft
  which takes place between the time any person boards the aircraft with
  the intention of flight until such time as all such persons have
  disembarked, in which:
a) a person is fatally or seriously injured as a result of

being in the aircraft, or
direct contact with any part of the aircraft, including parts which have become detached from the aircraft, or
direct exposure to jet blast,

except when the injuries are from natural causes, self inflicted or
  inflicted by other persons, or when the injuries are to stowaways
  hiding outside the areas normally available to the passengers and
  crew: or
b) the aircraft sustains damage or structural failure which:

adversely affects the structural strength, performance or flight characteristics of the aircraft, and
would normally require major repair or replacement of the affected component,

except for engine failure or damage. when the damage is limited to the
  engine, its cowlings or accessories: or for damage limited to
  propellers, wing tips, antennas, tires, brakes, fairings, small dents
  or puncture holes in the aircraft skin: or
c) the aircraft is missing or is completely inaccessible.
Note I.-- For statistical uniformity only, an injury resulting in
  death within thirty days of the date of the accident is classified as
  a fatal injury by ICAO.
Note 2.-- An aircraft is considered to be missing when the official
  search has been terminated and the wreckage has not been located.

And then there is

Incident. An occurrence, other than an accident, associated with the
  operation of an aircraft which affects or could affect the safety of
  operation.

They do also define 'serious incident', but simply as an incident which was nearly an accident; which is still an 'incident' by the definition above.

Falstro, you beat me by minutes again. If you want to incorporate more sources: AvHerald FAQ, BFU FAQ and the SKYbrary. +1 for being faster and posting the same I was gonna quote... ;)

@SentryRaven Cool :) First rep in months :D Yeah, AvHerald does list one more though, "Crash", which is not an official one. Crashes, even ones that completely obliterate the aircraft, are still labeled "accidents" in ICAO speak.

There's also NTSB 830 for notification. And interestingly enough, how much do you know about Accident and Incident reporting? http://www.aopa.org/asf/asfquiz/quizzes.cfm?SA=Quizzes&QuizId=100

@Shawn Note that NTSB 830 is only a US rule.

@Lnafziger, yes but if you're a pilot in the US, I believe it would supersede ICAO. Regardless, it pretty much says exactly the same thing. :-)


text:
Why are sidestep ILS minima not used in EASA-land? (specific example: EGKK)
If you are not aware, London Gatwick (aka EGKK) has a setup with a primary air carrier runway and a backup runway immediately next to it, such that only one runway can be used at a time.
The main runway 8R/26L (South) has full HIALS (ALSF-2 in FAA parlance) with CAT III ILS as well as RNAV (LNAV/VNAV, no SBAS/LPV) and plated SRA non-precision approaches; however, the backup runway 8L/26R (North) only has RNAV and SRA approaches, and no ALS.
Similar runway configurations in the US (KEWR aka Newark Int'l is similar save for having a crosswind runway) allow what is called a sidestep ILS procedure, where the main ILS is flown to higher (nonprecision) minima and then a maneuver is executed on short final to "slide" over to the other runway after visual contact with both runways has been achieved. From AIM 5-4-19:

5−4−19. Side−step Maneuver
a. ATC may authorize a standard instrument
  approach procedure which serves either one of
  parallel runways that are separated by 1,200 feet or
  less followed by a straight−in landing on the adjacent
  runway.
b. Aircraft that will execute a side−step maneuver
  will be cleared for a specified approach procedure
  and landing on the adjacent parallel runway.
  Example, “cleared ILS runway 7 left approach,
  side−step to runway 7 right.” Pilots are expected to
  commence the side−step maneuver as soon as
  possible after the runway or runway environment is
  in sight. Compliance with minimum altitudes
  associated with stepdown fixes is expected even after
  the side−step maneuver is initiated.
  NOTE−
  Side−step minima are flown to a Minimum Descent
  Altitude (MDA) regardless of the approach authorized.
c. Landing minimums to the adjacent runway will
  be based on nonprecision criteria and therefore higher
  than the precision minimums to the primary runway,
  but will normally be lower than the published circling
  minimums.

Why has the UK not published similar minima for Gatwick's ILS?  The existing OCHs for the secondary runway RNAV approaches are in the 650' range -- if the Newark ILS sidestep minima are any indication, it'd be possible to obtain lower minima for a sidestep approach to the EGKK secondary runway than are currently available from the RNAV or SRA approaches, and it would require no new navaids to be put into service.
Are sidestep approaches verboten in JAR-land? Is there some terrain or obstacle factor that I'm not seeing that makes a sidestep ILS approach into EGKK problematic or not desirable relative to the current RNAV approaches to the secondary runway?  Or can the ICAO/CAA format for approach plates not represent sidestep minima?

I think the core part of your question is, "Are sidestep approaches verboten in JAR-land?". The only online references seem to be for the US, so rather than focusing the question on one airport, you might want to ask the simpler question first of whether they even exist in the UK (or outside the US, or under EASA, or however you prefer to phrase it).

@mins -- there are RNAV approaches published for it as well

You use circling minima for sidestep manoeuvres. While not commonly practiced, they may be requested by the pilot, have done so many times when LEMD (MAD) is in N config, saves 20min taxi-time...

After a lot of Googling, it looks to me like a side-step ILS approach is exclusively a US term and - at least practically speaking - it doesn't exist in the rest of the world. There are almost no relevant search hits for the term in other countries; Transport Canada includes it in their glossary but it's a direct copy from the FAA's P/CG and is noted as a US term:

U.S.: A visual maneuver [sic] accomplished by a pilot at the
  completion of an instrument approach to permit a straight-in landing
  on a parallel runway not more than 1200 ft to either side of the
  runway to which the instrument approach was conducted.

I did find out that some other countries use the term swingover for more or less the same thing, but the only two extensive sources I found are in German: IVAO Deutschland and wikipedia.de. Neither of them quotes a regulatory or ICAO source. The IVAO page says that pilots usually ask for a swingover, whereas in the US - at least based on what I found in forums - ATC will request it from the pilot.
But even if you're willing to accept that "it's a US thing", it doesn't explain why only the US has side-step approaches. I can think of a fairly vague reason, but I may be completely wrong. Side-step minima are different, as the ATC orders (section 4-8-7) note:

Side-step maneuvers require higher weather minima/MDA. These higher
  minima/MDA are published on the instrument approach charts

That means it takes actual work to create side-step minima, you can't just use them 'for free' from another ILS approach. So my guess here is that the US simply has - or, historically, had - better ILS and weather reporting facilities than many other countries do, as well as more resources directed at defining approaches and more flights going into busy airports. In other words, side-step approaches are more practical, 'affordable' and useful for the US than for other countries. But that's entirely my own speculation, and if someone can find a documented reason that would be great.


text:
How is a type rating administered for aircraft that do not comply with 91.109?
Let's say you have a demilitarized A-10 (this isn't too farfetched an idea, as this SDSM&T proposal for a replacement thunderstorm research aircraft demonstrates).  With an empty weight twice the 12,500 pound limit, it clearly requires a type rating; however, there was only one two-seat A-10 (the YA-10B) ever built, and it likely isn't airworthy any longer.  (It is on static display at Edwards AFB.)
So, how would you train a civil pilot to get their A-10 type rating?  Would it be a simulator-only exercise, or a long ground school followed by a solo signoff?

Is your question pertaining specifically to de-mil'ed aircraft or more generally about single seat aircraft that might require a type rating (though I can't think of anything that might meet the criteria and NOT be a former military aircraft)? If it's de-mil'ed aircraft, they're normally registered as experimentals, so I don't think the normal type rating stuff applies.

@habu -- I was asking more generically, but using the A-10 as an example type

@Federico -- fixed link

The short of it is that most such ex-military aircraft, and replicas built new to spec on these designs, do not have a "type" as defined by the FAA at all. Because the absence of a type means the aircraft can't be certified as airworthy in the normal way, and pilots of these aircraft cannot receive a type rating to fly them, the certification of aircraft and pilot is a bit different.
The aircraft must first be issued an FAA "Special Airworthiness Certificate". This is essentially a slightly more rigorous form of airworthiness inspections for type-rated aircraft and virtually identical to that for experimental and/or home-built aircraft, resulting in the certification of the craft as airworthy in general even though it does not fall into a predefined aircraft type for which FAA instructors can issue type ratings.
The airman, because he can't be certified to fly a non-existent FAA aircraft type, must receive a special rating certification called a "Letter of Authorization", allowing the pilot to fly aircraft of a specific model, and/or a "set" of aircraft that have similar configuration, power, weight and other operational specifications and limits (but that aren't similar or common enough for a type rating). The training required for an LOA includes a combination of ground school and flight school containing information and in-flight training on the specific model to be authorized. But, when it is not possible or practical to do in-flight training in the exact model of aircraft to be authorized (usually because the aircraft in question is a single-seater with no two-seat configuration available), flight training in a "similar" aircraft can be a substitute. Pilots of vintage single-seat warplanes like P-51s typically get their flight training for the category in something similar to what military pilots of the day would have used, such as an AT-6. If the flight school just happens to have a Twin Mustang laying around, that would be even better, and also more directly applicable to multi-engine warbirds like the P-38.
Back to your example, say you get your hands on a "de-fanged" A-10 (which would require a ton of ballast weight to be added, literally; the GAU-8 weighs about as much as a Cadillac, but I digress). All flying examples are single-seaters; however, the avionics, especially of the original A-10A without the glass cockpit upgrade of the PEUP program, are comparable to any 70's-era jet trainer. So, you could receive flight training in a T-33, which is a trainer-compatible straight-wing turbojet with more similarities in its flight characteristics to the A-10 than differences. Coupled with ground instruction and/or simulator time on the specific systems of the A-10 (Which won't include any weapons integration, but honestly for the A-10A that was a single FLIR display and the arming/firing switches, and the C variant only upgraded that to a pair of MFDs; other than relative positioning, the flight instruments of the A-10 would be familiar to any PPL), you could be certified to fly your A-10 solo without any flight hours in an A-10 specifically.
The same might apply to aircraft that do have two-seater variants but where the flight school is unable to procure one. If you won the Powerball, and put a chunk of that money into your very own milsurp F-15C (\$38 million a pop back when they were being made and that's in late 1970s dollars), it's highly unlikely your local flight school would be willing to pony up for an F-15D two-seat configuration to train you on it (unless you bought the plane for them with another big chunk of your lottery winnings). They might, however, have a T-38 in their inventory or be able to loan one from the nearby naval air station, which would give you a primer into the capabilities of a multi-engine turbofan ex-military fighter. Honestly, though, if you wanted to fly an F-15, you'll probably want a two-seater, and your CPL, so you could give rides to paying customers and offset the cost of running this beast (typical fuel load without droptanks, 13,500 lbs which is about 1,985 gallons. With Jet A running about \$4.85/gallon, the cost of a fillup would be somewhere in the $10,000 neighborhood which would give you a cruising range of about 1,000 miles, so you could offer this as a special type of jet taxi).
Here's some more reading on the subject: FAA Flight Systems Information Management System - 8900.1 V5 Chapter 9 Sec 2 - Airman Qualification Requirements for Aircraft for Which the Operating Limitations Require an FAA‑issued Authorization to Act as Pilot in Command

Might be hard to keep the A-10 radar, as they didn't have one originally.  If the new mission is thunderstorm research, it'd probably get something new, tailored exactly to that mission anyway.  Nice that you'd have all the space/weight of the missing GAU-8 available to put it in!

That's right, the A-10A didn't even have its own laser designator or FLIR. Some A-10 pilots would have their crew chiefs intentionally neuter a Maverick (typically leaving the ignition/rail-release circuits disconnected on the last missile to sequence) to keep that missile as a "poor-man's FLIR" to find targets for The Gun in low light. A-10Cs still don't have radar, but they do have their own FLIR and laser designator, plus a glass cockpit, GPS, JHMCS and other abilities needed for modern "smart" weaponry.


text:
What procedures are in place at London City Airport for emergencies after V1?
Given the challenging operating environment at EGLC, what procedures are in place for emergencies after V1. Is it possible to return to the airport?

London City certainly has its challenges, with a steep approach and high rise buildings in close vicinity to the short runway, at the same time you have all sorts of places to divert to: Southend to the east, Stanstead and Luton to the North, Heathrow to the west, Farnborough, Gatwick, the list goes on. All of these places have longer runways with less constrained areas and fields all around. North Weald and Biggin Hill could also be used in an emergency. By the time you have returned to LYC you could have reached one of those.
It depends on the severity of the situation; if you have a mechanical problem but can land safely then going back to LCY is convenient for your passengers, if you're on fire or have control problems you're better off an another airport.
It is certainly possible to return to the airport in an emergency, and it has been done at least once. In 2014 an Avro RJ85 returned to the airport after a part of a nacelle came off. The headline is misleading, it says part of the wing fell off but it was really a nacelle. This is sort of "emergency-lite" as the flight could not continue, but the condition of the airplane was good enough that a normal approach could be made and the passengers moved to another flight.
The same year an Avro RJ100 diverted to Stanstead after an engine fire.
So the wisdom of returning to London City in an emergency is entirely dependent on context like the condition of the aircraft, weather, etc.


text:
Is the pitch control output in PX4 autopilot inverted?
I am trying to translate controller diagram of the fixed wing PX4 attitude controller into mathematical form.
While going through the controller diagram Fixed-Wing Attitude Controller looking into PX4 source code for pitch control Ref I found the following output,
 _last_output = _bodyrate_setpoint * _k_ff * ctl_data.scaler +
                _rate_error * _k_p * ctl_data.scaler * ctl_data.scaler
                + _integrator;  //scaler is proportional to 1/airspeed

For understanding, I am keeping scaler as one and lateral states as zero, so that the last output which is the elevator deflection looks following.
_last_output = (ctl_data.pitch_setpoint - ctl_data.pitch )*_k_ff  +((ctl_data.pitch_setpoint - ctl_data.pitch) - ctl_data.body_y_rate) * _k_p  + integral((ctl_data.pitch_setpoint - ctl_data.pitch)*dt);

My doubt is if we want to pitch up, (pitch_setpoint-pitch) will be positive, and with all gain values being positive in PX4 controller, RHS is positive, but conventionally we give negative elevator deflection for pitch up.
How is this taken care in the PX4 firmware? Can anyone explain or give a clearer picture of how this is possible?
I may not be able to format the question very well but I have drawn a similar scenario in the picture attached.

What sort of vehicle will this autopilot be used for - is it a UAV, a manned aircraft, a quadcopter, or what?

Welcome to aviation stackexchange. While I answered your question, I would like to point out that drones.stackexchange might be a better place to ask these kind of questions, as this a drone autpilot.

@RalphJ I believe that is intended for use in unmanned vehicles. I have heard of this autopilot before used in drones and long-range RC planes. I’m fairly certain that it isn’t designed for a manned aircraft. (This specific one can also be used in other things; not just aircraft)

Normally deflections of control surfaces are defined such that if they are positive, they generate positive forces which result in negative angular rates. (Except for ailerons which generate differential forces. For consistency they also generate negative rates)
Therefore:

A positive elevator deflection generates a negative pitch rate (nose goes down)
A positive rudder deflection generates a negative yaw rate (nose goes to the left)
A positive aileron deflection generates a negative roll rate (aircraft rolls to the left)

This is in most cases the sign convention for control deflections.
I want to point out that this necessitates a sign flip for a standard PID loop as in your case. For PX4 autopilots a parameter exists which can flip the servo output of a given control channel for exactly this reason. This can be done for example via the QGC software.

So, does this sign flip always happen in PX4 if pitch setpoint is more than current pitch? Is it done after the "_last_output" variable is generated? If you could clarify a bit more.

If and when the sign flip has to happen, mainly depends of how you installed the servo motor in your aircraft. However, you can reverse the output via the PWM_MAIN_REV parameter. If you want to learn more about how the _last_output variable is propagated through the system, consider this help page https://docs.px4.io/main/en/concept/architecture.html#flight-stack . But the sign flip is not dependent on the output of the pid loop. It is either configured or not.


text:
How can I reduce the Short Period frequency of a Pitch Hold Auto-Pilot while maintaining stability?
I am working on a  Pitch Hold Auto-pilot for F-104, which has the following damping characteristics;

which clearly shows that it has degenerated and unstable phugoid mode. well, I made a SAS which consists of 2 loops / Feedbacks.
1) The angle of attack feedback to increase the Cm alpha or static margin of the aircraft
2 Pitch rate feedback to dampen the short period mode.
but it has eventually increased the natural frequency to almost 365 rad/s as shown below,

but this frequency is not according to the handling qualities as it should be less than 3 rad /s.
what feedbacks should I try so that all the states are stable as well as desired handling qualities can be achieved?
states are velocity, angle of attack, pitch, pitch rate.
Simulink Model of SAS:

Root Locus of the outer Loop:

How can i decrease the frequency to the desired range keeping it stable and keeping in mind that it was unstable first.
Also, with not much decrease in damping as it should be greater than 0.5.(short period mode)
Phugoid mode >0.04

Seems like your alpha feedback is too large?

then what would be the best way to compensate it?

Can you provide the full state space matrices you're using?

I have provided please check as i redited it.

You seem to have too high an alpha feedback. For intuitive understanding, alpha feedback mainly increases the pitch stiffness, analogous to increasing the static margin; pitch rate feedback mainly increases the pitch damping. For your purpose, you would need to significantly reduce the alpha feedback.
For example, with your provided state space model,
$$\dot{x}=Ax+Bu$$
using a linear feedback,
$$u=Kx$$
where
$$K=\begin{bmatrix}0 & 0.5 & 0.25 & 0 \end{bmatrix}$$
satisfies your damping ratio requirements. SP frequency is 3.9 rad/s, SP damping is 0.53, Phugoid frequency is 0.023 rad/s, Phugoid damping is 0.14.

yes it Worked but the frequency is little bit higher

@Adeel But it's much better than your 364rad/s. For high HQR, you typically want higher SP frequency. That being said, you can keep lowering the alpha feedback and increasing the pitch damping if you want to make further adjustment.


text:
Who controls airspace and time in my area on helicopters?
I live in Newport Beach which is located in Orange County, California. I recently moved to an area where helicopters fly once in a while at 2-3 am above my house. Since I live on a hill, the sound is pretty loud and it wakes me up at night.
I was wondering where can I find more information about who controls the airspace in my area in regards to helicopters and how I look up the rules. I've googled a few things but can't find any answers. I'm not sure if it is the FAA or the county or the city or the state. Any pointers in the right direction would be appreciated.

Not many pilots will take commercial or recreational flights at 2 or 3am.  As Zeiss said, these flights are likely military in nature, or possibly Flight-for-Life / Air Ambulance flights.  It is extremely unlikely you can do anything about them.

Like others said, if it's military you're probably out of luck. If it's police, they don't fall under federal jurisdiction, so it'd be up to whatever department is operating the helicopter, city, county, etc. At 2am it's unlikely to be civil aircraft, but if it is and they are operating out of John Wayne Airport, their noise abatement rules are published here.

Given that you're near a couple military bases, there's every likelihood (especially if the choppers you hear are heavy models like Chinooks or Apaches) that they're from one of those bases.  There is little chance a complaint will change anything if that's the case; training exercises that don't cause a hazard to civilians are pretty well immune to civilian comment.
To start, you'd have to be able to positively identify the craft type (likely to be very difficult in the dead of night) and give exact time and location.
If they're non-military, you'd have to determine if they were in violation of FAA altitude, noise abatement, or restricted airspace limitations, or flying unsafely before a complaint to FAA authorities would stick -- once again, difficult to manage at that time of night.
Sorry to say, this might be why your new home was for sale.

yeah, i was wondering why the house comes with stingers.

You can use a service like FlightRadar24.com to see whether the flight is civilian or military. The military ones don't show up, but if military there is little you can do anyway. If it is civil you will see where it came from and where it is going. That might give you the airport to which you can complain.

What category does the local police fall under? and does that website track helicopters? I see commercial flights.

Helicopters on commercial flights -- charters, commuter flights -- ought to show up.  Unlikely to be instruction of private pleasure flights at 2-3 AM.  Police might not, but they only fly a couple types with rather distinctive rotor noise patterns, neither of which is used in common military operations.

@jason Anything non military will show up, including police in helicopters.

Looks like SOCAL Approach. I don't see a phone # on the chart tho.
https://skyvector.com/
Click on World VFR, then pan around to Los Angeles.
Try https://www.faa.gov/ for a phone number.
If you click on LA East Heli, you will also see quite a few H in a circle, those are heliports.  I see several for Police or Emergency use, I doubt you'll have much luck getting those curtailed.  And would you want to? What if you needed that service some day?

These 2 sites may be able to help you track them:

https://planefinder.net/
https://global.adsbexchange.com/VirtualRadar/desktop.html

Many here in New York and Long Island are faced with constant commuter helicopters. They seem to have all the freedom to destroy the public's quality of life. Over 80 000 complaints have been filed to our local officials, yet they have not done anything to re-route them!

Do you have a source for these complaints?